1. Field of the Invention
The present invention relates in general to the field of information handling system manufacture, and more particularly to information handling system anodized housing manufacture.
2. Description of the Related Art
As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems often include sensitive components that are enclosed in a metallic housing. Aluminum is one example of a metal having characteristics that provide an acceptable solution for an information handling system housing. Aluminum has good strength with relatively light weight to help reduce the overall size and weight of an information handling system. Reduced size and weight are especially desirable characteristics for portable information handling systems, such as laptops, tablets and smartphones.
One difficulty with aluminum is that it oxidizes when exposed to the atmosphere. Oxidation of untreated aluminum by exposure to the atmosphere detracts from the appearance of the metal and makes the metal susceptible to physical damage and further decay over time. In order to protect aluminum and similar metals (such as magnesium, titanium, zinc, niobium and tantalum) from oxidation, the outer surface is typically passivated so that underlying metal will not oxidize. One common technique for passivation of aluminum and similar metals is anodizing the metal with electrolytic passivation to increase the thickness of the natural oxidation layer on the surface of the metal. The aluminum is the anode electrode in an electrically charged bath so that oxygen released by hydrolysis in the presence of an electrical charge forms aluminum oxide with micro-crystalline structures having shorter and more stable bonds.
Typical anodizing processes involve preliminary steps to clean the metal surface and chemically polish the surface, such as by soaking in a solvent bath to remove grease followed by soaking in a solvent bath to etch the metal. The prepared metal is then submerged in an electrolytic solution and exposed to an electric current with the metal acting as the anode of the current. Various types of anodizing aluminum use different types of electrolytic solutions, such as chromic acid type I anodizing or sulfuric acid type II and III anodizing. Anodizing of other metals use these and other electrolytic solutions. Once a desired oxidation layer thickness is formed on the aluminum surface, the surface is protected by dyeing and then sealing nano-pores formed during anodizing.
During the anodizing process, the bath that holds the metal is typically agitated with an airflow from a tube that has holes to allow air to pass into the bath. The air agitates the bath to help ensure that the metal has a consistent bath content across its surface. If an uneven bath content flows over the surface of the metal, the cosmetics of the final metal product can have inconsistencies, such as poor dye color distribution evidenced when mottling and uneven anodized thickness are present. Poor cosmetics of the final metal product due to an inconsistent bath content can be amplified by other process imperfections, such as residual internal stress from metal stamping, inconsistent sanding or polishing, uneven bead blasting or other mechanical steps that adversely affect the surface prior to anodizing.